Shareholders' Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Feb. 17, 2014	Feb. 19, 2013	Feb. 18, 2013 Share repurchase program 2013 [Member]	Feb. 18, 2013 Share Repurchase Program 2012 [Member]	May 31, 2012 Share Repurchase Program 2012 [Member]
Equity, Class of Treasury Stock [Line Items]
Dividends on Common Stock, minimum					$ 0.14	$ 0.12
Dividends on Common Stock, maximum					$ 0.16	$ 0.14
Authorized amount to be repurchased							$ 750.0		$ 1,000.0
Repurchase of shares	573,881	2,784,000	2,010,304	5,761,104
Repurchases of shares, value	43.5	150.8	153.1	306.3
Remaining authorized repurchase capacity	$ 231.3		$ 231.3					$ 193.0